anton_ztalker

Thanks for your response. Sorry, I can't upload the program, because I'm not the author. And the program is awkward, this can be a cause of the error. I solved the problem as follows: set the check bit SB135 (COM Port 1, Data Receive) before sending the requests to Port 2 and reduced the baud rate to 9600.

In my project on the V120-22 I use 2 COM ports for RS485 Modbus communication. Port 2 - Master mode to communicate with another device, the Port 1 - Slave mode for communication with the upper level. After some time, the PLC stops responding via Port 1, while Port 2 is operating normally and ladder is operating normally too. Helps only restart the PLC. If Port 2 is disabled, then the connection through Port 1 is without failing. It seems, as if at the time of simultaneous access to the ports, there is a conflict. Why lost communication with Port 1? Ports settings: Port 2: 115200, 8, none, 2 Port 1: 57600, 8, none, 1 The request to Port 1 is sent after a pause of 10 ms after the last response Connection breaks after 2000-15000 requests Best regards, Anton